Device and method for assigning subframes as blank subframes

ABSTRACT

[Solution] There is provided a device including: an acquiring unit configured to acquire information about a plurality of small cells; and a control unit configured to assign blank subframes in which no signal is transmitted and received to each of the plurality of small cells. The control unit assigns the same subframes to one or more small cells that are a part of the plurality of small cells as the blank subframes and does not assign the same subframes to the remaining small cells among the plurality of small cells as the blank subframes.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application is a continuation of U.S. application Ser. No.15/303,443, filed Oct. 11, 2016, which is based on PCT filingPCT/JP2015/056429, filed Mar. 4, 2015, which claims priority to JP2014-104238, filed May 20, 2014, the entire contents of each areincorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a device.

BACKGROUND ART

Currently, in cellular systems, a small cell on/off technology is beingfocused on. Through the small cell on/off technology, an on/off state ofa small cell is adaptively switched and thus it is possible to reduceinterference with a neighbor cell of the small cell. Varioustechnologies for switching the on/off state of a small cell areproposed.

For example, in Patent Literature 1, a technology in which transmissionpower is controlled in an environment in which the on/off state of asmall cell is switched and thus coverage is ensured is disclosed.

CITATION LIST Patent Literature

Patent Literature 1 JP 2012-231366A

SUMMARY OF INVENTION Technical Problem

However, there is a possibility of communication quality of a terminaldevice deteriorating when a small cell is switched to an off state. Forexample, when a small cell positioned at a cell edge of a macro cell isswitched to the off state and a terminal device that was performingcommunication in the small cell performs communication in the macrocell, communication quality of the terminal device may significantlydeteriorate. That is, there is a possibility of a coverage hole beinggenerated when a small cell is switched to the off state.

Therefore, it is preferable to provide a mechanism through which it ispossible to suppress deterioration of communication quality of aterminal device while reducing interference from a small cell.

Solution to Problem

According to the present disclosure, there is provided a deviceincluding: an acquiring unit configured to acquire information about aplurality of small cells; and a control unit configured to assign blanksubframes in which no signal is transmitted and received to each of theplurality of small cells. The control unit assigns the same subframes toone or more small cells that are a part of the plurality of small cellsas the blank subframes and does not assign the same subframes to theremaining small cells among the plurality of small cells as the blanksubframes.

According to the present disclosure, there is provided a deviceincluding: an acquiring unit configured to acquire informationindicating decision of switching of a small cell from an on state to anoff state; and a control unit configured to request that the switchingbe canceled.

According to the present disclosure, there is provided a deviceincluding: a control unit configured to decide to switch a small cellfrom an on state to an off state; and an acquiring unit configured toacquire a request that the switching be canceled. The control unitcancels the switching in response to the request.

Advantageous Effects of Invention

According to the present disclosure described above, it is possible tosuppress deterioration of communication quality of a terminal devicewhile reducing interference from a small cell. Note that the effectsdescribed above are not necessarily limitative. With or in the place ofthe above effects, there may be achieved any one of the effectsdescribed in this specification or other effects that may be graspedfrom this specification.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an explanatory diagram for describing an example of a smallcell.

FIG. 2 is an explanatory diagram for describing an example of a smallcell cluster.

FIG. 3 is a sequence diagram illustrating an example of a schematic flowof an on/off process of a small cell.

FIG. 4 is a sequence diagram illustrating an example of a schematic flowof an on/off process of a small cell when a DRS is used.

FIG. 5 is an explanatory diagram for describing an example of ameasurement gap.

FIG. 6 is an explanatory diagram for describing a first scenario ofcarrier aggregation (CA).

FIG. 7 is an explanatory diagram for describing a second scenario ofcarrier aggregation (CA).

FIG. 8 is an explanatory diagram for describing a third scenario ofcarrier aggregation (CA).

FIG. 9 is an explanatory diagram for describing an example of an on/offstate of a small cell.

FIG. 10 is an explanatory diagram illustrating an example of a schematicconfiguration of a communication system according to a first embodiment.

FIG. 11 is a block diagram illustrating an example of a configuration ofa control entity according to the first embodiment.

FIG. 12 is an explanatory diagram for describing a first example ofassigning blank subframes.

FIG. 13 is an explanatory diagram for describing a second example ofassigning blank subframes.

FIG. 14 is an explanatory diagram for describing a third example ofassigning blank subframes.

FIG. 15 is an explanatory diagram for describing a fourth example ofassigning blank subframes.

FIG. 16 is a sequence diagram illustrating an example of a schematicflow of a process according to the first embodiment.

FIG. 17 is an explanatory diagram illustrating an example of a schematicconfiguration of a communication system according to a secondembodiment.

FIG. 18 is a block diagram illustrating an example of a configuration ofa terminal device according to a second embodiment.

FIG. 19 is a block diagram illustrating an example of a configuration ofa control entity according to the second embodiment.

FIG. 20 is a sequence diagram illustrating an example of a schematicflow of a process according to the second embodiment.

FIG. 21 is a sequence diagram illustrating an example of a schematicflow of a cancellation determining process according to the secondembodiment.

FIG. 22 is a block diagram illustrating an example of a schematicconfiguration of a server.

FIG. 23 is a block diagram illustrating a first example of a schematicconfiguration of an eNB.

FIG. 24 is a block diagram illustrating a second example of theschematic configuration of the eNB.

FIG. 25 is a block diagram illustrating an example of a schematicconfiguration of a smartphone.

FIG. 26 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus.

DESCRIPTION OF EMBODIMENT(S)

Hereinafter, (a) preferred embodiment(s) of the present disclosure willbe described in detail with reference to the appended drawings. In thisspecification and the drawings, elements that have substantially thesame function and structure are denoted with the same reference signs,and repeated explanation is omitted.

In this specification and the appended claims, elements havingsubstantially the same function and structure may in some cases bedistinguished by different letters appended to the same sign. Forexample, multiple elements having substantially the same function andstructure are distinguished as small base stations 15A, 15B and 15C asnecessary. On the other hand, when none of the multiple elements havingsubstantially the same function and structure is particularlydistinguished, only the same sign will be given. For example, the smallbase stations 15A, 15B and 15C will be simply designated as the smallbase station 15 when not particularly distinguished.

The description will proceed in the following order.

-   1. Introduction

1.1. Related technology

1.2. Problems related to switching of on/off state of small cell

-   2. Schematic configuration of communication system according to    present embodiment-   3. First embodiment

3.1. Configuration of communication system

3.2. Configuration of control entity

3.3. Process flow

-   4. Second embodiment

4.1. Configuration of communication system

4.2. Configuration of terminal device

4.3. Configuration of control entity

4.4. Process flow

-   5. Application examples

5.1. Application examples for control entity

5.2. Application examples for terminal device

-   6. Conclusion

1. INTRODUCTION

First, a technology related to an embodiment of the present disclosureand problems related to switching of an on/off state of a small cellwill be described with reference to FIG. 1 to FIG. 9.

<1.1. Related Technology>

A technology related to an embodiment of the present disclosure will bedescribed with reference to FIG. 1 to FIG. 8. Specifically, a smallcell, a measurement and carrier aggregation will be described.

(Small cell)

(a) Small Cell

A small cell is a cell smaller than a macro cell. For example, the smallcell partially or entirely overlaps the macro cell. Hereinafter, anexample of the small cell will be described with reference to FIG. 1.

FIG. 1 is an explanatory diagram for describing an example of a smallcell. Referring to FIG. 1, a macro base station 11, a macro cell 13, asmall base station 15 and a small cell 17 are shown. The macro basestation 11 is a base station of the macro cell 13. The small basestation 15 is a base station of the small cell 17. In other words, themacro cell 13 is a coverage area of the macro base station 11 (that is,a communication area), and the small cell 17 is a coverage area of thesmall base station 15 (that is, a communication area).

A base station of LTE is referred to as an evolved node B (eNB). Here, amacro base station of LTE is referred to as a macro eNB, and a smallbase station of LTE is referred to as a small eNB. In addition, aterminal device of LTE is referred to as user equipment (UE).

(b) Small Cell Cluster

Small cells arranged at a high density form a small cell cluster.Hereinafter, an example of the small cell cluster will be described withreference to FIG. 2.

FIG. 2 is an explanatory diagram for describing an example of a smallcell cluster. Referring to FIG. 2, the macro base station 11, the macrocell 13 and the small cell 17 are shown. For example, small cells 17arranged at a high density form a small cell cluster 19.

(c) Small Cell On/Off

In a case in which small cells are arranged at a high density,inter-cell interference causes a serious problem. In general, the smallbase station transmits a cell-specific reference signal (CRS) regardlessof the presence or absence of traffic of the small cell. In the case inwhich small cells are arranged at a high density, it is known that a CRScauses large interference in a neighbor cell. Therefore, varioustechnologies for reducing interference are being studied.

As a technology for reducing such inter-cell interference, a small cellon/off technology has currently been focused on. In the small cellon/off technology, an on/off state of a small cell is adaptivelyswitched, and thus it is possible to suppress interference in asurrounding cell of the small cell. While a trigger for switching anon/off state of the small cell has not yet been specifically decided, atrigger for switching based on, for example, a traffic amount,association of a terminal device, or arrival of a packet is beingstudied. Hereinafter, an example of a small cell on/off procedure willbe described with reference to FIG. 3.

FIG. 3 is a sequence diagram illustrating an example of a schematic flowof a small cell on/off process. The small cell on/off process is aprocess that is disclosed in R1-134318 of the Third GenerationPartnership Project (3GPP). When data to be transmitted is generated,the UE transmits an uplink signal to a macro eNB of a macro cell that isa serving cell (S1001). Then, the macro eNB searches for a small eNB inan off state that is positioned around the UE, and instructs theappropriate small eNB to switch to an on state when there is anappropriate small eNB (S1003). Then, the small eNB performs switchingfrom the off state to the on state (S1005). Then, the small eNBtransmits downlink signals such as a primary synchronization signal(PSS), a secondary synchronization signal (SSS), a cell-specificreference signal (CRS) and a physical broadcast channel (PBCH) signal(S1007). In addition, the UE performs a cell search and RRM measurement(S1009), and performs measurement reporting to the macro eNB (S1011).Then, a handover of the UE from the macro cell to the small cell isperformed (S1013). Then, the UE and the small eNB perform an accessprocedure (S1015) and perform data transmission (S1017).

According to the procedure shown in FIG. 3, it is possible to switch anon/off state of a small cell. However, according to the procedure, atransition time may become relatively longer. That is, according to theprocedure, a time from when a terminal device attempts to transmit datauntil the terminal device actually transmits the data may becomerelatively longer. Therefore, large improvement of throughput isdifficult. In order to improve the transition time, while the small cellis in the off state, a measurement process that serves as a main delayfactor is preferably performed by the terminal device.

(d) Discovery Reference Signal

Introduction of a discovery reference signal (DRS) is being studied inorder to reduce the transition time. The DRS enables measurement of asmall cell in the off state. The DRS is also referred to as a discoverysignal (DS). A small base station (for example, a small eNB) transmits aDRS while a small cell (or a small base station) is in the off state,and a terminal device (for example, UE) performs measurement based on aDRS. Hereinafter, an example of a small cell on/off procedure when a DRSis used will be described with reference to FIG. 4.

FIG. 4 is a sequence diagram illustrating an example of a schematic flowof a small cell on/off process when a DRS is used. The small cell on/offprocess is a process that is disclosed in R1-134318 of the 3GPP. A macroeNB instructs a small eNB to transmit a DS (S1031), and the small eNBtransmits the DS in downlink (S1033). The UE performs measurement basedon the DS (S1035) and reports a result of the measurement to the macroeNB (that is, an eNB of a macro cell that is a serving cell) (S1037).The UE and the small eNB perform data transmission through subsequentprocedures (S1041 to S1049) (S1051).

According to the procedure shown in FIG. 4, while the small cell is inthe off state, the terminal device can perform measurement. Therefore,the transition time is removed and throughput may be improved.

As various technologies for reducing interference, enhancement on atransmission side and a reception side such as muting, multiple instanceand interference cancellation is also being studied.

(Measurement) (a) CRS Measurement

In LTE, a terminal device performs measurement based on a CRStransmitted by a base station. Specifically, the terminal devicereceives a CRS transmitted by a base station and thus performsmeasurement of quality of a propagation path between the base stationand the terminal device. The measurement is referred to as “radioresource management (RRM) measurement,” or is simply referred to as“measurement.”

A result of the measurement is used to select a cell for a terminaldevice. As a specific example, the result of the measurement is used forcell selection/cell reselection by a terminal device that is in a radioresource control (RRC) idle (RRC Idle) state. In addition, for example,the result of the measurement is reported to a base station by aterminal device that is in an RRC connected state and is used for ahandover decision by the base station.

(b) RSRP and RSRQ

In LTE, CRS measurement is measurement of reference signal receivedpower (RSRP) and/or reference signal received quality (RSRQ). In otherwords, a terminal device acquires RSRP and/or RSRQ as a result of themeasurement of the CRS. The RSRQ is calculated from the RSRP and areceived signal strength indicator (RSSI).

The RSRP is received power of a CRS for each single resource element.That is, the RSRP is an average value of received power of the CRS. Thereceived power of the CRS is obtained by detecting a correlation betweena reception signal in a resource element of the CRS and a known signalCRS. The RSRP corresponds to a desired signal “Signal (S).”

The RSSI is total power of signals for each Orthogonal FrequencyDivision Multiple Access (OFDMA) symbol. Therefore, the RSSI includes adesired signal, an interference signal and noise. That is, the RSSIcorresponds to “Signal (S)+Interference (I)+Noise (N).”

The RSRQ is RSRP/(RSRI/N). N denotes the number of resource blocks usedfor calculating an RSSI. The resource blocks are resource blocks thatare arranged in a frequency direction. Therefore, the RSRQ is a valuethat is obtained by dividing the RSRP using the RSRI for each resourceblock. That is, the RSRQ corresponds to asignal-to-interference-plus-noise ratio (SINR).

As described above, according to the measurement of the CRS, receivedpower (that is, RSRP) and received quality (that is, RSRQ) such as anSINR are obtained.

(c) Measurement Timing

Measurement of a frequency band that a terminal device uses is referredto as intra-frequency measurement. Conversely, measurement of afrequency band that a terminal device does not use is referred to asinter-frequency measurement.

The terminal device can receive a CRS transmitted in a frequency bandthat is used without switching a frequency of a radio frequency (RF)circuit. That is, it is unnecessary to switch a frequency of the RFcircuit for intra-frequency measurement.

Conversely, in order for the terminal device to receive a CRStransmitted in a frequency band that is not used, it is necessary toswitch a frequency of a radio frequency (RF) circuit. That is, it isnecessary to switch a frequency of the RF circuit for inter-frequencymeasurement. Therefore, a period called a measurement gap is used forinter-frequency measurement.

During the measurement gap, the base station does not transmit adownlink signal addressed to a terminal device. In addition, themeasurement gap is shared between the base station and the terminaldevice. For example, the base station transmits a message (for example,an RRC connection reconfiguration message) including informationindicating a measurement gap to the terminal device. For example, themeasurement gap is indicated by a measurement gap length (MGL), ameasurement gap repetition period (MGRP) and a gap offset. In addition,a combination of the MGL and the MGRP is determined as, for example, agap pattern. Hereinafter, an example of the measurement gap will bedescribed with reference to FIG. 5.

FIG. 5 is an explanatory diagram for describing an example of ameasurement gap. FIG. 5 shows a matrix including columns of radio frameswhose SFNs are 0 to 9 and rows of 10 subframes (subframes whose subframenumbers are 0 to 9) included in radio frames. In this example, the MGLis 6 milliseconds (ms), the MGRP is 40 ms, and the gap offset is 0.Therefore, the measurement gap has a length of 6 ms and appears every 40ms. More specifically, for example, six subframes whose subframe numbersare 0 to 5 among radio frames whose SFNs are 0, 4 and 8 are themeasurement gap. Inter-frequency measurement is performed during themeasurement gap.

(d) Measurement Reporting

The terminal device reports a measurement result to the base station.The reporting is referred to as measurement reporting.

The measurement reporting is periodic reporting or event-triggeredreporting. The periodic reporting is reporting that is performed at setperiods. Conversely, the event-triggered reporting is reporting that isperformed when a reporting event is generated. Reporting events A1 to A5are events associated with a handover within a system, and reportingevents B1 to B2 are events associated with a handover between systems.

TABLE 1 Event Type Description Event A1 Serving becomes better thanthreshold Event A2 Serving becomes worse than threshold Event A3Neighbour becomes offset better than serving Event A4 Neighbour becomesbetter than threshold Event A5 Serving becomes worse than threshold1 andneighbor becomes better than threshold2 Event B1 Inter RAT neighbourbecomes better than threshold

(Carrier Aggregation)

Carrier aggregation (CA) is a technology through which communication isperformed using a plurality of component carriers (CCs) at the sametime. The component carrier is a frequency band having a maximum of a 20MHz bandwidth. The carrier aggregation includes three scenarios.Hereinafter, three scenarios of the carrier aggregation will bedescribed with reference to FIG. 6 to FIG. 8.

FIG. 6 to FIG. 8 are explanatory diagrams for describing first to thirdscenarios of carrier aggregation (CA). As illustrated in FIG. 6, in thefirst scenario (intra-band contiguous) of CA, the terminal device usesCCs adjacent in the same operating. As illustrated in FIG. 7, in thesecond scenario (intra-band non-contiguous) of CA, the terminal deviceuses CCs that are not adjacent in the same operating. As illustrated inFIG. 8, in the third scenario (inter-band non-contiguous) of CA, theterminal device uses CCs that are not adjacent in different operating.

<1.2. Problems Related to Switching of On/Off State of Small Cell>

Next, problems related to switching of the on/off state of a small cellwill be described with reference to FIG. 9.

On/off state switching of a small cell is performed based on, forexample, a traffic load, a cell association of a terminal device and/ora packet arrival. For example, when there is a terminal device in thesmall cell, the small cell is specifically switched to the on state anda base station of the small cell communicates with the terminal device.Conversely, when there is no terminal device in the small cell, thesmall cell is switched to the off state in order to reduce unnecessaryinterference.

When the on/off state of the small cell is switched according to theabove-described criteria, although efficient on/off state switchingseems to be possible, this may not necessarily be the case. For example,in a case in which terminal devices are equally distributed at a lowdensity within a small cell cluster, the number of small cells that areswitched to the off state is small and interference is not easilyreduced. Hereinafter, this will be described with reference to aspecific example of FIG. 9.

FIG. 9 is an explanatory diagram for describing an example of the on/offstate of a small cell. Referring to FIG. 9, the macro base station 11,the macro cell 13, the small base stations 15A to 15F, the small cells17A to 17F and terminal devices 21A to 21F are shown. The small cells17A to 17C are included in a small cell cluster 19A. The small cells 17Dto 17F are included in a small cell cluster 19B. For example, in thesmall cell cluster 19A, since the terminal devices 21A to 21C arelocated in the small cells 17A to 17C, respectively, the small cells 17Ato 17C are switched to the on state. Therefore, in the small cellcluster 19A, interference is not suppressed. On the other hand, in thesmall cell cluster 19B, since the terminal devices 21D to 21F areconcentrated at the small cell 17F, the small cell 17F is switched tothe on state, and the small cells 17D and 17E are switched to the offstate. Therefore, in the small cell cluster 19B, interference issuppressed.

In the above-described case, for example, when the terminal device ishanded over to the macro cell, more small cells can be switched to theoff state. However, in such a technique, for example, when a small cellpositioned at a cell edge of the macro cell is switched to the off stateand the terminal device that was performing communication in the smallcell performs communication in the macro cell, communication quality ofthe terminal device may significantly deteriorate. That is, there is apossibility of a coverage hole being generated when the small cell isswitched to the off state.

Therefore, it is preferable to provide a mechanism through which it ispossible to reduce interference from the small cell and suppressdeterioration of communication quality of the terminal device.

3. FIRST EMBODIMENT

Next, a first embodiment of the present disclosure will be describedwith reference to FIG. 10 to FIG. 16.

<3.1. Schematic Configuration of Communication System>

First, a schematic configuration of a communication system 1 accordingto the first embodiment will be described with reference to FIG. 10.FIG. 10 is an explanatory diagram illustrating an example of a schematicconfiguration of the communication system 1 according to the firstembodiment. As illustrated in FIG. 10, the communication system 1includes a control entity 100 and a plurality of small base stations 31.The communication system 1 is a system supporting, for example, LTE,LTE-Advanced, or a communication standard equivalent thereto.

The small base station 31 is a base station of a small cell 33. Forexample, the small cell 33 is included in a small cell cluster 35. Forexample, the small base station 31 wirelessly communicates with aterminal device. Specifically, for example, the small base station 31transmits a downlink signal to the terminal device and receives anuplink signal from the terminal device.

The control entity 100 performs control of the small cell 33. Thecontrol entity 100 is, for example, an existing or new core networknode. Alternatively, the control entity 100 may be a base station.

Specifically, in the first embodiment, the control entity 100 assignsblank subframes in which no signal is transmitted and received to eachof the plurality of small cells 33. The control entity 100 assigns thesame subframes to one or more small cells 33 that are a part of theplurality of small cells 33 as the blank subframes and does not assignthe same subframes to the remaining small cells 33 among the pluralityof small cells 33 as the blank subframes. Accordingly, for example, itis possible to suppress deterioration of communication quality of theterminal device while reducing interference from a small cell.

<3.2. Configuration of Control Entity>

Next, an example of a configuration of the control entity 100 accordingto the first embodiment will be described with reference to FIG. 11 toFIG. 15. FIG. 11 is a block diagram illustrating an example of aconfiguration of the control entity 100 according to the firstembodiment. As illustrated in FIG. 11, the control entity 100 includes acommunication unit 110, a storage unit 120 and a processing unit 130.

(Communication Unit 110)

The communication unit 110 transmits and receives information. Forexample, the communication unit 110 transmits information to anothernode and receives information from the other node. For example, theother node includes a core network and a base station. As an example,the other node includes the small base station 31.

(Storage Unit 120)

The storage unit 120 temporarily or permanently stores programs and datafor operations of the control entity 100.

(Processing Unit 130)

The processing unit 130 provides various functions of the control entity100. The processing unit 130 includes an information acquiring unit 131and a control unit 133. Alternatively, the processing unit 130 mayfurther include a component other than these components. That is, theprocessing unit 130 may perform an operation other than operations ofthese components.

(Information Acquiring Unit 131)

The information acquiring unit 131 acquires information about theplurality of small cells 33 (hereinafter referred to as “small cellinformation”).

(a) Small Cell Information

For example, the small cell information includes identificationinformation for identifying each of the small cells 33. Morespecifically, for example, the identification information is a cell IDof each of the small cells 33. For example, cell IDs of the plurality ofsmall cells 33 are stored in the storage unit 120, and the informationacquiring unit 131 acquires a cell ID from the storage unit 120.

For example, the small cell information includes traffic amountinformation indicating an amount of traffic in each of the plurality ofsmall cells 33. For example, the small base station 31 of each of theplurality of small cells 33 transmits traffic amount informationindicating an amount of traffic in the small cell 33 to the controlentity 100, and the traffic amount information is stored in the storageunit 120. The information acquiring unit 131 acquires the traffic amountinformation from the storage unit 120 at any timing thereafter.

The small cell information is not limited to the above-describedexample. As an example, the small cell information may not include thetraffic amount information. As another example, the small cellinformation may further include another piece of information.

(b) Plurality of Small Cells

For example, the plurality of small cells 33 are a set of adjacent smallcells 33. More specifically, for example, the plurality of small cells33 are small cells 33 that are included in the same small cell cluster35. The plurality of small cells 33 may be all of the small cells 33that are included in the small cell cluster 35 or a part of the smallcells 33 that are included in the small cell cluster 35.

The plurality of small cells 33 may not be included in the small cellcluster, but may be a simple set of small cells.

(Control Unit 133)

The control unit 133 assigns blank subframes in which no signal istransmitted and received to each of the plurality of small cells 33. Thecontrol unit 133 assigns the same subframes to one or more small cells33 that are a part of the plurality of small cells 33 as the blanksubframes, and does not assign the same subframes to the remaining smallcells 33 among the plurality of small cells 33 as the blank subframes.Accordingly, for example, interference from the remaining small cells 33to the one or more small cells 33 may be removed. In addition, when thesmall cells 33 are not completely switched to the off state and do nottransmit a signal in a subframe unit, the terminal device can continuecommunication in the small cell 33. Therefore, deterioration ofcommunication quality of the terminal device may be suppressed.

(a) Amount of Blank Subframes Assigned to Small Cell

(a-1) Assignment Based on Amount of Traffic

For example, the control unit 133 assigns blank subframes to each of theplurality of small cells 33 based on an amount of traffic in each of theplurality of small cells 33.

More specifically, for example, the control unit 133 assigns fewer blanksubframes to the first small cell 33 having a greater amount of trafficamong the plurality of small cells 33 and assigns more blank subframesto the second small cell 33 having a smaller amount of traffic among theplurality of small cells 33. Hereinafter, this will be described withreference to a specific example of FIG. 12.

FIG. 12 is an explanatory diagram for describing a first example ofassigning blank subframes. As illustrated in FIG. 12, one radio frame(10 subframes) and five small cells 33A to 33E are shown. For example,an amount of traffic in the small cell 33B is greatest and an amount oftraffic in the small cell 33C is smallest. Therefore, for example, threesubframes (subframes 2 to 4) are assigned to the small cell 33B as blanksubframes and one subframe (a subframe 5) is assigned to the small cell33C as a blank subframe. Two subframes are assigned to each of the smallcell 33A, the small cell 33D and the small cell 33E as blank subframes.

Accordingly, for example, it is possible to use more radio resources inthe small cell 33 having a greater amount of traffic. Therefore, it ispossible to avoid generation of a great amount of delay in the smallcell 33 having a great amount of traffic.

(a-2) Equal Assignment

The control unit 133 may equally assign blank subframes to each of theplurality of small cells 33. Hereinafter, this will be described withreference to a specific example of FIG. 13.

FIG. 13 is an explanatory diagram for describing a second example ofassigning blank subframes. As illustrated in FIG. 13, one radio frame(10 subframes) and five small cells 33A to 33E are shown. For example,regardless of an amount of traffic in each of the small cells 33A to33E, two subframes are assigned to each of the small cells 33A to 33E asblank subframes.

Accordingly, for example, it is possible to assign blank subframeswithout collecting information about the small cell 33. That is,assigning blank subframes may be performed more easily.

(b) Transmission of Signal in Same Subframes

(b-1) Case in which Transmission of Signal is Possible in One Small Cell

For example, the control unit 133 assigns the same subframes to smallcells excluding one small cell among the plurality of small cells as theblank subframes and does not assign the same subframes to the one smallcell as the blank subframes. That is, in the same subframes, a signal istransmitted only in one small cell.

For example, referring again to FIG. 12, each subframe is assigned onlyto one small cell 33. In addition, referring again to FIG. 13, eachsubframe is assigned only to one small cell 33.

Accordingly, for example, interference between the plurality of smallcells 33 may be removed.

(b-2) Case in which Transmission of Signal is Possible in Two or MoreSmall Cells

The control unit 133 assigns each of at least one subframe to smallcells excluding two or more small cells among the plurality of smallcells as the blank subframe, and may not assign each of at least onesubframe to the two or more small cells as the blank subframe. That is,in at least one subframe, a signal may be transmitted in two or moresmall cells. Hereinafter, this will be described with reference to aspecific example of FIG. 14.

FIG. 14 is an explanatory diagram for describing a third example ofassigning blank subframes. As illustrated in FIG. 14, one radio frame(10 subframes) and five small cells 33A to 33E are shown. For example, asubframe 2 is assigned to two small cells (the small cells 33A and 33B)as a blank subframe. In addition, a subframe 4 is assigned to two smallcells (the small cells 33B and 33C) as a blank subframe. In addition, asubframe 5 is assigned to three small cells (the small cells 33B, 33Cand 33D) as a blank subframe. A subframe 8 is assigned to two smallcells (the small cells 33D and 33E) as a blank subframe.

Accordingly, for example, more opportunities to transmit a signal areprovided in the individual small cell 33. As a result, throughput may beimproved.

(c) No Assignment of Specific Subframe

The control unit 133 may not assign a specific subframe to any of thesmall cells 33 as the blank subframe.

For example, the specific subframe may be a subframe in which asynchronization signal (SS) is transmitted. Hereinafter, this will bedescribed with reference to a specific example of FIG. 15.

FIG. 15 is an explanatory diagram for describing a fourth example ofassigning blank subframes. As illustrated in FIG. 15, one radio frame(10 subframes) and five small cells 33A to 33E are shown. For example,since a synchronization signal is transmitted in a subframe 0 and asubframe 5, the subframe 0 and the subframe 5 are not assigned to any ofthe small cells 33 as blank subframes. On the other hand, the othersubframes are assigned as blank subframes.

Accordingly, for example, the terminal device can be synchronized in thesmall cell 33.

For example, as described above, the control unit 133 assigns the blanksubframes to each of the plurality of small cells. For example, thecontrol unit 133 notifies the small base station 31 of each of theplurality of small cells 33 of the assigned blank subframes.Accordingly, the small base station 31 may apply the assigned blanksubframes. As a result, interference between the small cells 33 may besuppressed.

<3.3. Process Flow>

Next, an example of a process according to the first embodiment will bedescribed with reference to FIG. 16.

FIG. 16 is a sequence diagram illustrating an example of a schematicflow of a process according to the first embodiment.

The small base station 31 transmits traffic amount informationindicating an amount of traffic in the small cell 33 to the controlentity 100 (S201).

The control entity 100 (the control unit 133) assigns blank subframes inwhich no signal is transmitted and received to each of the plurality ofsmall cells 33 (S203). For example, the control entity 100 assigns theblank subframes to each of the plurality of small cells 33 based on anamount of traffic in each of the plurality of small cells 33.

The control entity 100 (the control unit 133) notifies the small basestation 31 of each of the plurality of small cells 33 of the assignedblank subframes (S205).

The small base station 31 applies the assigned blank subframes (S207).As a result, for example, the small base station 31 does not transmitand receive a signal in the assigned blank subframes.

The control entity 100 may perform the above process, for example, foreach set of a plurality of small cells.

(Other Variations)

The control entity 100 may assign the blank subframes to each of theplurality of small cells 33 regardless of the amount of traffic. In thiscase, the traffic amount information may not be transmitted to thecontrol entity 100 by the small base station 31. As an example, thecontrol entity 100 may equally assign the blank subframes to each of theplurality of small cells 33.

In addition, the small base station 31 may transmit another piece ofinformation to the control entity 100 instead of the traffic amountinformation or along with the traffic amount information. For example,the small base station 31 may transmit information indicating anassociation of the terminal device and/or a packet arrival to thecontrol entity 100.

In addition, the control entity 100 may decide to switch the on/offstate of the small cell.

4. SECOND EMBODIMENT

Next, a second embodiment of the present disclosure will be describedwith reference to FIG. 17 to FIG. 21.

<4.1. Schematic Configuration of Communication System>

First, a schematic configuration of a communication system 2 accordingto the second embodiment will be described with reference to FIG. 17.FIG. 17 is an explanatory diagram illustrating an example of a schematicconfiguration of the communication system 2 according to the secondembodiment. As illustrated in FIG. 17, the communication system 2includes a terminal device 300 and a control entity 400.

The terminal device 300 wirelessly communicates with a base station. Forexample, the terminal device 300 receives a downlink signal from thebase station and transmits an uplink signal to the base station.

The control entity 400 performs control of a small cell. The controlentity 400 is, for example, an existing or new core network node.Alternatively, the control entity 400 may be the base station.

Specifically, in the second embodiment, the control entity 400 decidesto switch the small cell from the on state to the off state. Theterminal device 300 acquires information indicating the decision ofswitching the small cell from the on state to the off state and requeststhat the switching be canceled. The control entity 400 cancels theswitching in response to the request to cancel the switching.Accordingly, for example, it is possible to suppress deterioration ofcommunication quality of the terminal device while reducing interferencefrom the small cell.

<4.2. Configuration of Terminal Device>

Next, an example of a configuration of the terminal device 300 accordingto the second embodiment will be described with reference to FIG. 18.FIG. 18 is a block diagram illustrating an example of a configuration ofthe terminal device 300 according to the second embodiment. Asillustrated in FIG. 18, the terminal device 300 includes an antenna unit310, a wireless communication unit 320, a storage unit 330 and aprocessing unit 340.

(Antenna Unit 310)

The antenna unit 310 emits a signal to be output by the wirelesscommunication unit 320 into space as radio waves. In addition, theantenna unit 310 converts the spatial radio waves into a signal andoutputs the signal to the wireless communication unit 320.

(Wireless Communication Unit 320)

The wireless communication unit 320 transmits and receives signals. Forexample, the wireless communication unit 320 receives a downlink signalfrom the base station and transmits an uplink signal to the basestation.

(Storage Unit 330)

The storage unit 330 temporarily or permanently stores programs and datafor operations of the terminal device 300.

(Processing Unit 340)

The processing unit 340 provides various functions of the terminaldevice 300. The processing unit 340 includes an information acquiringunit 341 and a control unit 343. Alternatively, the processing unit 340may further include a component other than these components. That is,the processing unit 340 may perform an operation other than operationsof these components.

(Information Acquiring Unit 341)

The information acquiring unit 341 acquires information indicating thedecision of switching the small cell from the on state to the off state(hereinafter referred to as “switching information”).

(a) Small Cell

For example, the small cell is a serving cell. Further, when theterminal device 300 supports, for example, carrier aggregation, thesmall cell is, for example, a primary cell of carrier aggregation.

The small cell is not limited to the above-described example. Forexample, the small cell may be a secondary cell rather than the primarycell. Alternatively, the small cell may be a cell (for example, aneighbor cell) other than the serving cell.

(b) On/Off State

For example, the “on state” of a small cell is a state in which a basestation of the small cell transmits and receives signals (a data signaland a control signal) in the small cell.

For example, the “off state” of a small cell is a state in which a basestation of the small cell does not transmit and receive signals exceptsome control signals (for example, a DRS) in the small cell.Alternatively, the “off state” of a small cell may be a state in which abase station of the small cell does not transmit and receive signals inthe small cell at all.

(c) Specific Technique

For example, the control entity 400 transmits the switching informationto the terminal device 300 through a serving base station of theterminal device 300 when the switching is decided. Specifically, forexample, the control entity 400 transmits a message of an upper layer(for example, Non-Access Stratum (NAS)) including the switchinginformation to the terminal device 300. Alternatively, the controlentity 400 may transmit the switching information to the serving basestation of the terminal device 300, and the base station may transmitthe switching information to the terminal device 300. The switchinginformation is received by the terminal device 300 and is stored in thestorage unit 330. The information acquiring unit 341 acquires theswitching information from the storage unit 330 at any timingthereafter.

(Control Unit 343)

The control unit 343 requests that the switching be canceled (that is,the switching of the small cell from the on state to the off state).

(a) Predetermined Condition

For example, when a predetermined condition regarding a result ofmeasurement performed by the terminal device 300 is satisfied, thecontrol unit 343 requests the cancellation. Accordingly, for example, arequest for cancellation is suppressed. Therefore, the small cell isswitched to the off state, and interference from the small cell may bereduced.

For example, the predetermined condition is a condition that ameasurement result of the small cell be more favorable than a firstthreshold and a measurement result of each of the other cells be lessfavorable than a second threshold.

More specifically, for example, the measurement result is referencesignal received power (RSRP) or reference signal received quality(RSRQ). In addition, the predetermined condition is a condition that ameasurement result of the small cell be greater than the first thresholdand a measurement result of the other cells be smaller than the secondthreshold. That is, the predetermined condition is a condition thatcommunication quality of the small cell be favorable and communicationquality of the other cells be unfavorable.

Accordingly, for example, when the small cell is switched to the offstate and thus communication quality of the terminal device 300 isassumed to be unfavorable, the switching may be cancelled. Therefore,deterioration of communication quality of the terminal device 300 may besuppressed.

The other cells include, for example, a macro cell and other smallcells.

(b) Specific Technique

For example, the control unit 343 transmits a cancellation requestmessage for requesting the cancellation through the antenna unit 310 andthe wireless communication unit 320.

For example, the control unit 343 transmits the cancellation requestmessage to the control entity 400 through the serving base station.Alternatively, the control unit 343 transmits the cancellation requestmessage to the serving base station, and the serving base station maytransmit the cancellation request message or a message similar theretoto the control entity 400.

As described above, the cancel is requested. Accordingly, for example,the small cell maintains the on state without switching to the off stateas necessary. Therefore, deterioration of communication quality of theterminal device 300 may be suppressed. In addition, interference fromthe small cell may be suppressed according to the switching of theon/off state of the small cell.

<4.3. Configuration of Control Entity>

Next, an example of a configuration of the control entity 400 accordingto the second embodiment will be described with reference to FIG. 19.FIG. 19 is a block diagram illustrating an example of a configuration ofthe control entity 400 according to the second embodiment. Asillustrated in FIG. 19, the control entity 400 includes a communicationunit 410, a storage unit 420 and a processing unit 430.

(Communication Unit 410)

The communication unit 410 transmits and receives information. Forexample, the communication unit 410 transmits information to anothernode and receives information from the other node. For example, theother node includes a core network, a base station and a terminaldevice. As an example, the other node includes a small base station andthe terminal device 300.

(Storage Unit 420)

The storage unit 420 temporarily or permanently stores programs and datafor operations of the control entity 400.

(Processing Unit 430)

The processing unit 430 provides various functions of the control entity400. The processing unit 430 includes an information acquiring unit 431and a control unit 433. Alternatively, the processing unit 430 mayfurther include a component other than these components. That is, theprocessing unit 430 may perform an operation other than operations ofthese components.

(Information Acquiring Unit 431) (a) Request to Cancel

The information acquiring unit 431 acquires a request to cancelswitching of the small cell from the on state to the off state.

For example, the request refers to a cancellation request message forrequesting the cancel. For example, the cancellation request message istransmitted to the control entity 400 by the terminal device 300.Alternatively, the cancellation request message may be transmitted tothe control entity 400 by the base station according to a request fromthe terminal device 300.

(b) Small Cell Onformation

For example, the information acquiring unit 431 acquires informationabout a small cell (hereinafter referred to as “small cellinformation”).

For example, the small cell information includes information indicatinga cell ID of a small cell, an amount of traffic in a small cell, a cellassociation of a terminal device and/or a packet arrival.

For example, a small base station of the small cell transmits the smallcell information to the control entity 400, and the control entity 400receives the small cell information. Then, the small cell information isstored in the storage unit 420. The information acquiring unit 431acquires the small cell information at any timing thereafter.

(Control Unit 433) (a) Decision of Switching

The control unit 433 decides to switch the on/off state of the smallcell.

For example, the control unit 433 decides to switch the small cell fromthe on state to the off state. Specifically, for example, the controlunit 433 decides the switching based on the small cell information.

Further, for example, the control unit 433 notifies the terminal device300 of the decided switching. For example, the control unit 433transmits information indicating the decided switching (that is,switching information) to the terminal device 300 through the servingbase station of the terminal device 300 when the switching is decided.Specifically, for example, the control unit 433 transmits a message ofan upper layer (for example, NAS) including the switching information tothe terminal device 300 through the serving base station. Alternatively,the control unit 433 transmits the switching information to the servingbase station of the terminal device 300, and the serving base stationmay transmit the switching information (or information similar thereto)to the terminal device 300.

(b) Cancellation of Switching

The control unit 433 cancels the switching in response to the request.

For example, the terminal device 300 transmits a cancellation requestmessage for requesting the cancellation. Then, the control unit 433cancels the switching according to the cancellation request message.

<4.4. Process Flow>

Next, an example of a process according to the second embodiment will bedescribed with reference to FIG. 20 and FIG. 21.

(Overall Process Flow)

FIG. 20 is a sequence diagram illustrating an example of a schematicflow of a process according to the second embodiment.

A small base station transmits information about a small cell (that is,small cell information) to a control entity 500 (S501).

The control entity 400 (the control unit 433) decides to switch thesmall cell from the on state to the off state (S503). For example, thecontrol entity 400 decides the switching based on the small cellinformation.

Then, the control entity 400 (the control unit 433) notifies theterminal device 300 of the decided switching (S505).

Then, the terminal device 300 (the control unit 343) performs acancellation determining process (S510). That is, the terminal device300 determines whether to request that the switching be canceled.Specifically, for example, the terminal device 300 determines whether apredetermined condition regarding a result of measurement performed bythe terminal device 300 is satisfied. Then, for example, the terminaldevice 300 determines to request that the switching be canceled.

The terminal device 300 (the control unit 343) requests that theswitching be canceled (that is, switching of the small cell from the onstate to the off state) (S521).

Then, the control entity 400 (the control unit 431) cancels theswitching (S523).

(Cancellation Determining Process)

FIG. 21 is a sequence diagram illustrating an example of a schematicflow of a cancellation determining process according to the secondembodiment.

The control unit 343 determines whether a measurement result of a smallcell is more favorable than the first threshold (S511).

When the measurement result is less favorable than the first threshold(NO in S511), the control unit 343 decides not to request that switchingbe canceled (S513). Then, the process ends.

On the other hand, when the measurement result is more favorable thanthe first threshold (YES in S511), the control unit 343 determineswhether a measurement result of each of the other cells is lessfavorable than the second threshold (S515).

When the measurement result is less unfavorable than the secondthreshold (NO in S515), the control unit 343 decides not to request thatswitching be canceled (S513). Then, the process ends.

On the other hand, when the measurement result is less favorable thanthe second threshold (YES in S515), the control unit 343 decides torequest that switching be canceled (S517). Then, the process ends.

5. APPLICATION EXAMPLES

The technology according to the present disclosure is applicable tovarious products. For example, the control entity (that is, the controlentity 100 or the control entity 400) may be implemented as any type ofserver such as a tower server, a rack server or a blade server. Inaddition, at least a part of components of the control entity may beimplemented in a module (for example, an integrated circuit module thatincludes a single die or a card or a blade that is inserted into a slotof a blade server) mounted in a server.

The control entity (i.e., the control entity 100 or the control entity400) may also be implemented, for example, as any type of evolved Node B(eNB) such as macro eNBs and small eNBs. Small eNBs may cover smallercells than the macrocells of pico eNBs, micro eNBs, or home (femt) eNBs.Instead, the control entity may be implemented as another type of basestation such as Nodes B or base transceiver stations (BTSs). The controlentity may include the main apparatus (which is also referred to as basestation apparatus) that controls wireless communication and one or moreremote radio heads (RRHs) that are disposed at different locations fromthat of the main apparatus. Further, various types of terminals as willbe discussed later may temporarily or semi-persistently execute the basestation function to operate as the control entity. Further, at leastpart of components of the control entity may be implemented in a basestation device or a module for the base station device.

The terminal device 300 may be implemented as a mobile terminal such assmartphones, tablet personal computers (PCs), notebook PCs, portablegame terminals, portable/dongle mobile routers, and digital cameras, oran in-vehicle terminal such as car navigation apparatuses. The terminaldevice 300 may also be implemented as a terminal (which is also referredto as machine type communication (MTC) terminal) that performs machineto machine (M2M) communication. Furthermore, at least part of componentsof the terminal device 300 may be implemented as a module (e.g.integrated circuit module constituted with a single die) that is mountedon these terminals.

<5.1. Application Examples for Control Entity> First Application Example

FIG. 22 is a block diagram illustrating an example of a schematicconfiguration of a server 700 to which the technology according to thepresent disclosure may be applied. The server 700 includes a processor701, a memory 702, a storage 703, a network interface 704, and a bus706.

The processor 701 may be, for example, a central processing unit (CPU)or a digital signal processor (DSP), and controls various functions ofthe server 700. The memory 702 includes a random access memory (RAM) anda read only memory (ROM), and stores a program executed by the processor701 and data. The storage 703 can include a storage medium such assemiconductor memories and hard disks.

The network interface 704 is a wired communication interface forconnecting the server 700 to a wired communication network 705. Thewired communication network 705 may be a core network such as evolvedpacket cores (EPCs), or a packet data network (PDN) such as theInternet.

The bus 706 connects the processor 701, the memory 702, the storage 703,and the network interface 704 to each other. The bus 706 may include twoor more buses each having different speed (e.g. high speed bus and lowspeed bus).

In the server 700 illustrated in FIG. 22, one or more components (theinformation acquiring unit 131 and/or the control unit 133) included inthe processing unit 130 described above with reference to FIG. 11 may bemounted in the processor 701. As an example, a program causing theprocessor to function as one or more of the components above (that is, aprogram causing the processor to perform the operation of one or more ofthe components above) may be installed in the server 700, and theprocessor 701 may execute the program. As another example, the server700 may include a module including the processor 701 and the memory 702,and one or more of the components above may be mounted in the module. Inthis case, the module may store the program causing the processor tofunction as one or more of the components above in the memory 702, andthe program may be executed by the processor 701. As described above,the server 700 or the module may be provided as an apparatus includingone or more of the components above, and the program causing theprocessor to function as one or more of the components above may beprovided. A readable recording medium in which the program is recordedmay be provided. For these points, one or more components (theinformation acquiring unit 431 and/or the control unit 433) included inthe processing unit 430 described with reference to FIG. 19 are similarto the one or more components included in the processing unit 130.

Second Application Example

FIG. 23 is a block diagram illustrating a first example of a schematicconfiguration of an eNB to which the technology according to the presentdisclosure may be applied. An eNB 800 includes one or more antennas 810and a base station apparatus 820. Each antenna 810 and the base stationapparatus 820 may be connected to each other via an RF cable.

Each of the antennas 810 includes a single or a plurality of antennaelements (e.g. a plurality of antenna elements constituting a MIMOantenna) and is used for the base station apparatus 820 to transmit andreceive a wireless signal. The eNB 800 may include the plurality of theantennas 810 as illustrated in FIG. 23, and the plurality of antennas810 may, for example, correspond to a plurality of frequency bands usedby the eNB 800. It should be noted that while FIG. 23 illustrates anexample in which the eNB 800 includes the plurality of antennas 810, theeNB 800 may include the single antenna 810.

The base station apparatus 820 includes a controller 821, a memory 822,a network interface 823, and a wireless communication interface 825.

The controller 821 may be, for example, a CPU or a DSP, and operatesvarious functions of an upper layer of the base station apparatus 820.For example, the controller 821 generates a data packet from data in asignal processed by the wireless communication interface 825, andtransfers the generated packet via the network interface 823. Thecontroller 821 may generate a bundled packet by bundling data from aplurality of base band processors to transfer the generated bundledpacket. The controller 821 may also have a logical function ofperforming control such as radio resource control, radio bearer control,mobility management, admission control, and scheduling. The control maybe performed in cooperation with a surrounding eNB or a core network.The memory 822 includes a RAM and a ROM, and stores a program executedby the controller 821 and a variety of control data (such as, forexample, terminal list, transmission power data, and scheduling data).

The network interface 823 is a communication interface for connectingthe base station apparatus 820 to the core network 824. The controller821 may communicate with a core network node or another eNB via thenetwork interface 823. In this case, the controller 821 may be mutuallyconnected to the eNB 800 and a core network node or another eNB througha logical interface (e.g. 51 interface or X2 interface). The networkinterface 823 may be a wired communication interface or a wirelesscommunication interface for wireless backhaul. When the networkinterface 823 is a wireless communication interface, the networkinterface 823 may use a higher frequency band for wireless communicationthan a frequency band used by the wireless communication interface 825.

The wireless communication interface 825 supports a cellularcommunication system such as long term evolution (LTE) or LTE-Advanced,and provides wireless connection to a terminal located within the cellof the eNB 800 via the antenna 810. The wireless communication interface825 may typically include a base band (BB) processor 826 and an RFcircuit 827. The BB processor 826 may, for example, performencoding/decoding, modulation/demodulation, multiplexing/demultiplexing,and the like, and performs a variety of signal processing on each layer(e.g. L1, medium access control (MAC), radio link control (RLC), andpacket data convergence protocol (PDCP)). The BB processor 826 may havepart or all of the logical functions as discussed above instead of thecontroller 821. The BB processor 826 may be a module including a memoryhaving a communication control program stored therein, a processor toexecute the program, and a related circuit, and the function of the BBprocessor 826 may be changeable by updating the program. The module maybe a card or blade to be inserted into a slot of the base stationapparatus 820, or a chip mounted on the card or the blade. Meanwhile,the RF circuit 827 may include a mixer, a filter, an amplifier, and thelike, and transmits and receives a wireless signal via the antenna 810.

The wireless communication interface 825 may include a plurality of theBB processors 826 as illustrated in FIG. 23, and the plurality of BBprocessors 826 may, for example, correspond to a plurality of frequencybands used by the eNB 800. The wireless communication interface 825 mayalso include a plurality of the RF circuits 827, as illustrated in FIG.23, and the plurality of RF circuits 827 may, for example, correspond toa plurality of antenna elements. FIG. 23 illustrates an example in whichthe wireless communication interface 825 includes the plurality of BBprocessors 826 and the plurality of RF circuits 827, but the wirelesscommunication interface 825 may include the single BB processor 826 orthe single RF circuit 827.

In the eNB 800 illustrated in FIG. 23, one or more components includedin the processing unit 130 described above with reference to FIG. 11(the information acquiring unit 131 and/or the control unit 133) may bemounted in the controller 821. Alternatively, at least some of thecomponents may be mounted in the wireless communication interface 825.As an example, the eNB 800 may be equipped with a module including someor all components of the wireless communication interface 825 (forexample, the BB processor 826) and/or the controller 821, and one ormore of the components above may be mounted in the module. In this case,the module may store a program causing the processor to function as oneor more of the components above (that is, a program causing theprocessor to perform the operation of one or more of the componentsabove) and execute the program. As another example, the program causingthe processor to function as one or more of the components above may beinstalled in the eNB 800, and the wireless communication interface 825(for example, the BB processor 826) and/or the controller 821 mayexecute the program. As described above, the eNB 800, the base stationapparatus 820, or the module may be provided as an apparatus includingone or more of the components above, and the program causing theprocessor to function as one or more of the components above may beprovided. A readable recording medium in which the program is recordedmay be provided. For these points, one or more components included inthe processing unit 430 described above with reference to FIG. 19 (theinformation acquiring unit 431 and/or the control unit 433) are the sameas one or more of the components above included in the processing unit130.

Third Application Example

FIG. 24 is a block diagram illustrating a second example of a schematicconfiguration of an eNB to which the technology according to the presentdisclosure may be applied. An eNB 830 includes one or more antennas 840,a base station apparatus 850, and an RRH 860. Each of the antennas 840and the RRH 860 may be connected to each other via an RF cable. The basestation apparatus 850 and the RRH 860 may be connected to each other bya high speed line such as optical fiber cables.

Each of the antennas 840 includes a single or a plurality of antennaelements (e.g. antenna elements constituting a MIMO antenna), and isused for the RRH 860 to transmit and receive a wireless signal. The eNB830 may include a plurality of the antennas 840 as illustrated in FIG.24, and the plurality of antennas 840 may, for example, correspond to aplurality of frequency bands used by the eNB 830. FIG. 24 illustrates anexample in which the eNB 830 includes the plurality of antennas 840, butthe eNB 830 may include the single antenna 840.

The base station apparatus 850 includes a controller 851, a memory 852,a network interface 853, a wireless communication interface 855, and aconnection interface 857. The controller 851, the memory 852, and thenetwork interface 853 are the same as the controller 821, the memory822, and the network interface 823 described with reference to FIG. 23.

The wireless communication interface 855 supports a cellularcommunication system such as LTE and LTE-Advanced, and provides wirelessconnection to a terminal located in a sector corresponding to the RRH860 via the RRH 860 and the antenna 840. The wireless communicationinterface 855 may typically include a BB processor 856. The BB processor856 is the same as the BB processor 826 described with reference to FIG.23 except that the BB processor 856 is connected to an RF circuit 864 ofthe RRH 860 via the connection interface 857. The wireless communicationinterface 855 may include a plurality of the BB processors 856, asillustrated in FIG. 24, and the plurality of BB processors 856 may, forexample, correspond to a plurality of frequency bands used by the eNB830 respectively. FIG. 24 illustrates an example in which the wirelesscommunication interface 855 includes the plurality of BB processors 856,but the wireless communication interface 855 may include the single BBprocessor 856.

The connection interface 857 is an interface for connecting the basestation apparatus 850 (wireless communication interface 855) to the RRH860. The connection interface 857 may be a communication module forcommunication on the high speed line which connects the base stationapparatus 850 (wireless communication interface 855) to the RRH 860.

The RRH 860 includes a connection interface 861 and a wirelesscommunication interface 863.

The connection interface 861 is an interface for connecting the RRH 860(wireless communication interface 863) to the base station apparatus850. The connection interface 861 may be a communication module forcommunication on the high speed line.

The wireless communication interface 863 transmits and receives awireless signal via the antenna 840. The wireless communicationinterface 863 may typically include the RF circuit 864. The RF circuit864 may include a mixer, a filter, an amplifier and the like, andtransmits and receives a wireless signal via the antenna 840. Thewireless communication interface 863 may include a plurality of the RFcircuits 864 as illustrated in FIG. 24, and the plurality of RF circuits864 may, for example, correspond to a plurality of antenna elements.FIG. 24 illustrates an example in which the wireless communicationinterface 863 includes the plurality of RF circuits 864, but thewireless communication interface 863 may include the single RF circuit864.

In the eNB 830 illustrated in FIG. 24, one or more components includedin the processing unit 130 described above with reference to FIG. 11(the information acquiring unit 131 and/or the control unit 133) may bemounted in the controller 851. Alternatively, at least some of thecomponents may be mounted in the wireless communication interface 855and/or the wireless communication interface 863. As an example, the eNB830 may be equipped with a module including some or all components ofthe wireless communication interface 855 (for example, the BB processor856) and/or the controller 851, and one or more of the components abovemay be mounted in the module. In this case, the module may store aprogram causing the processor to function as one or more of thecomponents above (that is, a program causing the processor to performthe operation of one or more of the components above) and execute theprogram. As another example, the program causing the processor tofunction as one or more of the components above may be installed in theeNB 830, and the wireless communication interface 855 (for example, theBB processor 856) and/or the controller 851 may execute the program. Asdescribed above, the eNB 830, the base station apparatus 850, or themodule may be provided as an apparatus including one or more of thecomponents above, and the program causing the processor to function asone or more of the components above may be provided. A readablerecording medium in which the program is recorded may be provided. Inthese points, one or more components included in the processing unit 430described above with reference to FIG. 19 (the information acquiringunit 431 and/or the control unit 433) are the same as one or more of thecomponents above included in the processing unit 130.

<5.2. Application Examples for Terminal Device> First ApplicationExample

FIG. 25 is a block diagram illustrating an example of a schematicconfiguration of a smartphone 900 to which the technology according tothe present disclosure may be applied. The smartphone 900 includes aprocessor 901, a memory 902, a storage 903, an external connectioninterface 904, a camera 906, a sensor 907, a microphone 908, an inputdevice 909, a display device 910, a speaker 911, a wirelesscommunication interface 912, one or more antenna switches 915, one ormore antennas 916, a bus 917, a battery 918, and a secondary controller919.

The processor 901 may be, for example, a CPU or a system on chip (SoC),and controls the functions of an application layer and other layers ofthe smartphone 900. The memory 902 includes a RAM and a ROM, and storesa program executed by the processor 901 and data. The storage 903 mayinclude a storage medium such as semiconductor memories and hard disks.The external connection interface 904 is an interface for connecting thesmartphone 900 to an externally attached device such as memory cards anduniversal serial bus (USB) devices.

The camera 906 includes an image sensor such as charge coupled devices(CCDs) and complementary metal oxide semiconductor (CMOS), and generatesa captured image. The sensor 907 may include a sensor group including,for example, a positioning sensor, a gyro sensor, a geomagnetic sensor,and an acceleration sensor. The microphone 908 converts a sound that isinput into the smartphone 900 to an audio signal. The input device 909includes, for example, a touch sensor which detects that a screen of thedisplay device 910 is touched, a key pad, a keyboard, a button, or aswitch, and accepts an operation or an information input from a user.The display device 910 includes a screen such as liquid crystal displays(LCDs) and organic light emitting diode (OLED) displays, and displays anoutput image of the smartphone 900. The speaker 911 converts the audiosignal that is output from the smartphone 900 to a sound.

The wireless communication interface 912 supports a cellularcommunication system such as LTE or LTE-Advanced, and performs wirelesscommunication. The wireless communication interface 912 may typicallyinclude the BB processor 913, the RF circuit 914, and the like. The BBprocessor 913 may, for example, perform encoding/decoding,modulation/demodulation, multiplexing/demultiplexing, and the like, andperforms a variety of types of signal processing for wirelesscommunication. On the other hand, the RF circuit 914 may include amixer, a filter, an amplifier, and the like, and transmits and receivesa wireless signal via the antenna 916. The wireless communicationinterface 912 may be a one-chip module in which the BB processor 913 andthe RF circuit 914 are integrated. The wireless communication interface912 may include a plurality of BB processors 913 and a plurality of RFcircuits 914 as illustrated in FIG. 25. FIG. 25 illustrates an examplein which the wireless communication interface 912 includes a pluralityof BB processors 913 and a plurality of RF circuits 914, but thewireless communication interface 912 may include a single BB processor913 or a single RF circuit 914.

Further, the wireless communication interface 912 may support othertypes of wireless communication system such as a short range wirelesscommunication system, a near field communication system, and a wirelesslocal area network (LAN) system in addition to the cellularcommunication system, and in this case, the wireless communicationinterface 912 may include the BB processor 913 and the RF circuit 914for each wireless communication system.

Each antenna switch 915 switches a connection destination of the antenna916 among a plurality of circuits (for example, circuits for differentwireless communication systems) included in the wireless communicationinterface 912.

Each of the antennas 916 includes one or more antenna elements (forexample, a plurality of antenna elements constituting a MIMO antenna)and is used for transmission and reception of the wireless signal by thewireless communication interface 912. The smartphone 900 may include aplurality of antennas 916 as illustrated in FIG. 25. FIG. 25 illustratesan example in which the smartphone 900 includes a plurality of antennas916, but the smartphone 900 may include a single antenna 916.

Further, the smartphone 900 may include the antenna 916 for eachwireless communication system. In this case, the antenna switch 915 maybe omitted from a configuration of the smartphone 900.

The bus 917 connects the processor 901, the memory 902, the storage 903,the external connection interface 904, the camera 906, the sensor 907,the microphone 908, the input device 909, the display device 910, thespeaker 911, the wireless communication interface 912, and the secondarycontroller 919 to each other. The battery 918 supplies electric power toeach block of the smartphone 900 illustrated in FIG. 25 via a feederline that is partially illustrated in the figure as a dashed line. Thesecondary controller 919, for example, operates a minimally necessaryfunction of the smartphone 900 in a sleep mode.

In the smartphone 900 illustrated in FIG. 25, one or more componentsincluded in the processing unit 340 described above with reference toFIG. 18 (the information acquiring unit 341 and/or the control unit 343)may be mounted in the wireless communication interface 912.Alternatively, at least some of the components may be mounted in theprocessor 901 or the secondary controller 919. As an example, thesmartphone 900 may be equipped with a module including some or allcomponents of the wireless communication interface 912 (for example, theBB processor 913), the processor 901, and/or the secondary controller919, and one or more of the components above may be mounted in themodule. In this case, the module may store a program causing theprocessor to function as one or more of the components above (that is, aprogram causing the processor to perform the operation of one or more ofthe components above) and execute the program. As another example, theprogram causing the processor to function as one or more of thecomponents above may be installed in the smartphone 900, and thewireless communication interface 912 (for example, the BB processor913), the processor 901, and/or the secondary controller 919 may executethe program. As described above, the smartphone 900 or the module may beprovided as an apparatus including one or more of the components above,and the program causing the processor to function as one or more of thecomponents above may be provided. A readable recording medium in whichthe program is recorded may be provided.

In the smartphone 900 illustrated in FIG. 25, for example, the wirelesscommunication unit 320 described above with reference to FIG. 18 may bemounted in the wireless communication interface 912 (for example, the RFcircuit 914). The antenna unit 310 may be mounted in the antenna 916.

Second Application Example

FIG. 26 is a block diagram illustrating an example of a schematicconfiguration of a car navigation apparatus 920 to which the technologyaccording to the present disclosure may be applied. The car navigationapparatus 920 includes a processor 921, a memory 922, a globalpositioning system (GPS) module 924, a sensor 925, a data interface 926,a content player 927, a storage medium interface 928, an input device929, a display device 930, a speaker 931, a wireless communicationinterface 933, one or more antenna switches 936, one or more antennas937, and a battery 938.

The processor 921 may be, for example, a CPU or an SoC, and controls thenavigation function and the other functions of the car navigationapparatus 920. The memory 922 includes a RAM and a ROM, and stores aprogram executed by the processor 921 and data.

The GPS module 924 uses a GPS signal received from a GPS satellite tomeasure the position (e.g. latitude, longitude, and altitude) of the carnavigation apparatus 920. The sensor 925 may include a sensor groupincluding, for example, a gyro sensor, a geomagnetic sensor, and an airpressure sensor. The data interface 926 is, for example, connected to anin-vehicle network 941 via a terminal that is not illustrated, andacquires data such as vehicle speed data generated on the vehicle side.

The content player 927 reproduces content stored in a storage medium(e.g. CD or DVD) inserted into the storage medium interface 928. Theinput device 929 includes, for example, a touch sensor which detectsthat a screen of the display device 930 is touched, a button, or aswitch, and accepts operation or information input from a user. Thedisplay device 930 includes a screen such as LCDs and OLED displays, anddisplays an image of the navigation function or the reproduced content.The speaker 931 outputs a sound of the navigation function or thereproduced content.

The wireless communication interface 933 supports a cellularcommunication system such as LTE or LTE-Advanced, and performs wirelesscommunication. The wireless communication interface 933 may typicallyinclude the BB processor 934, the RF circuit 935, and the like. The BBprocessor 934 may, for example, perform encoding/decoding,modulation/demodulation, multiplexing/demultiplexing, and the like, andperforms a variety of types of signal processing for wirelesscommunication. On the other hand, the RF circuit 935 may include amixer, a filter, an amplifier, and the like, and transmits and receivesa wireless signal via the antenna 937. The wireless communicationinterface 933 may be a one-chip module in which the BB processor 934 andthe RF circuit 935 are integrated. The wireless communication interface933 may include a plurality of BB processors 934 and a plurality of RFcircuits 935 as illustrated in FIG. 26. FIG. 26 illustrates an examplein which the wireless communication interface 933 includes a pluralityof BB processors 934 and a plurality of RF circuits 935, but thewireless communication interface 933 may be a single BB processor 934 ora single RF circuit 935.

Further, the wireless communication interface 933 may support othertypes of wireless communication system such as a short range wirelesscommunication system, a near field communication system, and a wirelessLAN system in addition to the cellular communication system, and in thiscase, the wireless communication interface 933 may include the BBprocessor 934 and the RF circuit 935 for each wireless communicationsystem.

Each antenna switch 936 switches a connection destination of the antenna937 among a plurality of circuits (for example, circuits for differentwireless communication systems) included in the wireless communicationinterface 933.

Each of the antennas 937 includes one or more antenna elements (forexample, a plurality of antenna elements constituting a MIMO antenna)and is used for transmission and reception of the wireless signal by thewireless communication interface 933. The car navigation apparatus 920includes a plurality of antennas 937 as illustrated in FIG. 26. FIG. 26illustrates an example in which the car navigation apparatus 920includes a plurality of antennas 937, but the car navigation apparatus920 may include a single antenna 937.

Further, the smartphone 920 may include the antenna 937 for eachwireless communication system. In this case, the antenna switch 936 maybe omitted from a configuration of the car navigation apparatus 920.

The battery 950 supplies electric power to each block of the carnavigation apparatus 930 illustrated in FIG. 26 via a feeder line thatis partially illustrated in the figure as a dashed line. The battery 950accumulates the electric power supplied from the vehicle.

In the car navigation apparatus 920 illustrated in FIG. 26, one or morecomponents included in the processing unit 340 described above withreference to FIG. 18 (the information acquiring unit 341 and/or thecontrol unit 343) may be mounted in the wireless communication interface933. Alternatively, at least some of the components may be mounted inthe processor 921. As an example, the car navigation apparatus 920 maybe equipped with a module including some or all components of thewireless communication interface 933 (for example, the BB processor934), and/or the processor 921, and one or more of the components abovemay be mounted in the module. In this case, the module may store aprogram causing the processor to function as one or more of thecomponents above (that is, a program causing the processor to performthe operation of one or more of the components above) and execute theprogram. As another example, the program causing the processor tofunction as one or more of the components above may be installed in thecar navigation apparatus 920, and the wireless communication interface933 (for example, the BB processor 934), and/or the processor 921 mayexecute the program. As described above, the car navigation apparatus920 or the module may be provided as an apparatus including one or moreof the components above, and the program causing the processor tofunction as one or more of the components above may be provided. Areadable recording medium in which the program is recorded may beprovided.

In the car navigation apparatus 920 illustrated in FIG. 26, for example,the wireless communication unit 320 described above with reference toFIG. 18 may be mounted in the wireless communication interface 933 (forexample, the RF circuit 935). The antenna unit 310 may be mounted in theantenna 937.

Further, the technique according to the present disclosure may beimplemented as an in-vehicle system (or a vehicle) 940 including one ormore blocks of the above-described car navigation apparatus 920, anin-vehicle network 941 and a vehicle side module 942. The in-vehiclesystem (or the vehicle) 940 may be provided as an apparatus includingone more of the components above (the information acquiring unit 341and/or the control unit 343). The vehicle side module 942 generatesvehicle side data such as vehicle speed, engine speed and failureinformation and outputs the generated data to the in-vehicle network961.

11. CONCLUSION

Each communication apparatus and each process according to theembodiments of the present disclosure have been described above withreference to FIGS. 9 to 26.

First Embodiment

In the first embodiment, the control entity 100 includes the informationacquiring unit 131 configured to acquire information about a pluralityof small cells and the control unit 133 configured to assign blanksubframes in which no signal is transmitted and received to each of theplurality of small cells. The control unit 133 assigns the samesubframes to one or more small cells that are a part of the plurality ofsmall cells as the blank subframes and does not assign the samesubframes to the remaining small cells among the plurality of smallcells as the blank subframes.

Accordingly, for example, it is possible to suppress deterioration ofcommunication quality of the terminal device while reducing interferencefrom the small cell. More specifically, for example, interference fromthe remaining small cells to the one or more small cells may be removed.In addition, when the small cells are not completely switched to the offstate and do not transmit a signal in a subframe unit, the terminaldevice can continue communication in the small cell.

Therefore, deterioration of communication quality of the terminal devicemay be suppressed.

Second Embodiment

In the second embodiment, the terminal device 300 includes theinformation acquiring unit 341 configured to acquire informationindicating decision of switching the small cell from the on state to theoff state and the control unit 343 configured to request that theswitching be canceled.

In addition, in the second embodiment, the control entity 400 includesthe control unit 433 configured to decide to switch the small cell fromthe on state to the off state and the acquiring unit 431 configured toacquire a request that the switching be canceled. The control unit 433cancels the switching in response to the request.

Accordingly, for example, it is possible to suppress deterioration ofcommunication quality of the terminal device while reducing interferencefrom the small cell. More specifically, for example, the small cellmaintains the on state without switching to the off state as necessary.Therefore, deterioration of communication quality of the terminal device300 may be suppressed. In addition, interference from the small cell maybe suppressed according to the switching of the on/off state of thesmall cell.

The preferred embodiment of the present disclosure has been describedabove with reference to the accompanying drawings, whilst the presentdisclosure is not limited to the above examples. A person skilled in theart may find various alterations and modifications within the scope ofthe appended claims, and it should be understood that they willnaturally come under the technical scope of the present disclosure.

For example, while an example in which a communication system supportsLTE or LTE-A has been described in embodiments of the presentdisclosure, the present disclosure is not limited thereto. For example,the communication system may be a system that supports anothercommunication standard.

Further, it is not always necessary to execute the processing steps inthe processing in the present specification in chronological order inorder described in the flowcharts or the sequence diagrams. For example,the processing steps in the above-described processing may be executedin order different from the order described in the flowcharts or thesequence diagrams or may be executed in parallel.

Further, it is also possible to create a computer program for making aprocessor (such as, for example, a CPU and a DSP) provided atapparatuses (such as, for example, the control entity, the terminaldevice, or the modules thereof) in the present specification function ascomponents (such as, for example, an information acquiring unit and thecontrol unit) of the above-described apparatuses (in other words, acomputer program for making the processor execute operation of thecomponents of the above-described apparatuses). Further, it is alsopossible to provide a recording medium having the above-describedcomputer program recorded therein. Further, it is also possible toprovide an apparatus (such as, for example, a finished product and amodule (such as parts, processing circuits and chips) for the finishedproduct) including a memory having the above-described computer programstored therein and one or more processors which can execute theabove-described computer program. Further, a method including theoperation of the components (for example, an information acquiring unitand the control unit) of the above-described apparatuses is included inthe technique according to the present disclosure.

In addition, the effects described in the present specification aremerely illustrative and demonstrative, and not limitative. In otherwords, the technology according to the present disclosure can exhibitother effects that are evident to those skilled in the art along with orinstead of the effects based on the present specification.

Additionally, the present technology may also be configured as below.

-   (1)

A device including:

an acquiring unit configured to acquire information about a plurality ofsmall cells; and

a control unit configured to assign blank subframes in which no signalis transmitted and received to each of the plurality of small cells,

wherein the control unit assigns the same subframes to one or more smallcells that are a part of the plurality of small cells as the blanksubframes and does not assign the same subframes to the remaining smallcells among the plurality of small cells as the blank subframes.

-   (2)

The device according to (1),

wherein the control unit assigns the blank subframes to each of theplurality of small cells based on an amount of traffic in each of theplurality of small cells.

-   (3)

The device according to (2),

wherein the control unit assigns fewer blank subframes to a first smallcell having a greater amount of traffic among the plurality of smallcells and assigns more blank subframes to a second small cell having asmaller amount of traffic among the plurality of small cells.

-   (4)

The device according to (1),

wherein the control unit equally assigns the blank subframes to each ofthe plurality of small cells.

-   (5)

The device according to any one of (1) to (4),

wherein the control unit does not assign a specific subframe to any ofthe small cells as the blank subframe.

-   (6)

The device according to (5),

wherein the specific subframe is a subframe in which a synchronizationsignal is transmitted.

-   (7)

The device according to any one of (1) to (6),

wherein the control unit assigns the same subframes to small cellsexcluding one small cell among the plurality of small cells as the blanksubframes, and does not assign the same subframes to the one small cellas the blank subframes.

-   (8)

The device according to any one of (1) to (6),

wherein the control unit assigns each of at least one subframe to smallcells excluding two or more small cells among the plurality of smallcells as the blank subframe, and does not assign each of the at leastone subframe to the two or more small cells as the blank subframe.

-   (9)

The device according to any one of (1) to (8),

wherein the plurality of small cells are a set of adjacent small cells.

-   (10)

The device according to (9)

wherein the plurality of small cells are small cells that are includedin the same small cell cluster.

-   (11)

The device according to any one of (1) to (10),

wherein the control unit notifies a base station of each of theplurality of small cells of the assigned blank subframes.

-   (12)

A device including:

an acquiring unit configured to acquire information indicating decisionof switching of a small cell from an on state to an off state; and

a control unit configured to request that the switching be canceled.

-   (13)

The device according to (12),

wherein, when a predetermined condition regarding a result ofmeasurement performed by a terminal device is satisfied, the controlunit requests the cancellation.

-   (14)

The device according to (13),

wherein the predetermined condition is a condition that a measurementresult of the small cell be more favorable than a first threshold and ameasurement result of each of the other cells be less favorable than asecond threshold.

-   (15)

The device according to (14),

wherein the measurement result is reference signal received power (RSRP)or reference signal received quality (RSRQ), and

the predetermined condition is a condition that the measurement resultof the small cell be greater than the first threshold and themeasurement result of the other cells is smaller than the secondthreshold.

-   (16)

The device according to (14) or (15),

wherein the other cells include a macro cell and other small cells.

-   (17)

The device according to any one of (12) to (16),

wherein the small cell is a serving cell.

-   (18)

The device according to any one of (12) to (17),

wherein the device is a terminal device or a module for a terminaldevice.

-   (19)

A device including:

a control unit configured to decide to switch a small cell from an onstate to an off state; and

an acquiring unit configured to acquire a request that the switching becanceled,

wherein the control unit cancels the switching in response to therequest.

-   (20)

The device according to (19),

wherein the control unit notifies a terminal device of the decision ofthe switching.

-   (21)

A method including:

acquiring information about a plurality of small cells; and

assigning, by a processor, blank subframes in which no signal istransmitted and received to each of the plurality of small cells,

wherein the assigning of the blank subframes to each of the plurality ofsmall cells includes assigning the same subframes to one or more smallcells that are a part of the plurality of small cells as the blanksubframes and not assigning the same subframes to the remaining smallcells among the plurality of small cells as the blank subframes.

-   (22)

A program for causing a processor to execute:

acquiring information about a plurality of small cells; and

assigning blank subframes in which no signal is transmitted and receivedto each of the plurality of small cells,

wherein the assigning of the blank subframes to each of the plurality ofsmall cells includes assigning the same subframes to one or more smallcells that are a part of the plurality of small cells as the blanksubframes and not assigning the same subframes to the remaining smallcells among the plurality of small cells as the blank subframes.

-   (23)

A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

acquiring information about a plurality of small cells; and

assigning blank subframes in which no signal is transmitted and receivedto each of the plurality of small cells,

wherein the assigning of the blank subframes to each of the plurality ofsmall cells includes assigning the same subframes to one or more smallcells that are a part of the plurality of small cells as the blanksubframes and not assigning the same subframes to the remaining smallcells among the plurality of small cells as the blank subframes.

-   (24)

A method including:

acquiring information indicating decision of switching of a small cellfrom an on state to an off state; and

requesting, by a processor, that the switching be canceled.

-   (25)

A program for causing a processor to execute:

acquiring information indicating decision of switching of a small cellfrom an on state to an off state; and

requesting that the switching be canceled.

-   (26)

A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

acquiring information indicating decision of switching of a small cellfrom an on state to an off state; and

requesting that the switching be canceled.

-   (27)

A method including:

deciding, by a processor, to switch a small cell from an on state to anoff state; and

acquiring a request that the switching be canceled,

wherein the switching is cancelled in response to the request.

-   (28)

A program for causing a processor to execute:

deciding to switch a small cell from an on state to an off state; andacquiring a request that the switching be canceled,

wherein the switching is cancelled in response to the request.

-   (29)

A readable recording medium having a program recorded thereon, theprogram causing a processor to execute:

deciding to switch a small cell from an on state to an off state; and

acquiring a request that the switching be canceled,

wherein the switching is cancelled in response to the request.

REFERENCE SIGNS LIST

-   1 communication system-   2 communication system-   100 control entity-   131 information acquiring unit-   133 control unit-   300 terminal device-   341 information acquiring unit-   343 control unit-   400 control entity-   431 information acquiring unit-   433 control unit

1. A control apparatus controlling one or more base station apparatusesserving one or more cells, the control apparatus comprising: aninterface configured to communicate with a base station apparatus; andcircuitry configured to: receive, via the interface, cell informationfrom the base station apparatus, the cell information including one ormore cell identities respectively corresponding to the one or morecells; decide whether a state of each cell of the one or more cells isto be off or on; assign, to the one or more cells, one or more subframesin which one or more synchronization signals are not transmitted, theone or more synchronization signals being transmitted on other subframesthan the assigned one or more subframes; and notify the base stationapparatus of information indicating the assigned one or more subframeswhere the one or more synchronization signals are not transmitted. 2.The control apparatus according to claim 1, wherein the controlapparatus is another base station apparatus.
 3. The control apparatusaccording to claim 1, wherein the circuitry is further configured todecide, whether the state of each cell of the one or more cells is to beoff or on, based on a traffic load.
 4. A base station apparatus fromamong one or more base station apparatuses controlled by a controlapparatus, the base station comprising: an interface configured tocommunicate with the control apparatus; and circuitry configured to:serve one or more cells; and send, via the interface, cell informationto the control apparatus, the cell information including one or morecell identities respectively corresponding to the one or more cells,wherein a state of each cell of the one or more cells is decided to beoff or on by the control apparatus, one or more subframes, in which oneor more synchronization signals are not transmitted, are assigned to theone or more cells by the control apparatus, the one or moresynchronization signals being transmitted on other subframes than theassigned one or more subframes, and the circuitry is further configuredto receive, from the control apparatus via the interface, informationindicating the assigned one or more subframes where the one or moresynchronization signals are not transmitted.
 5. The base stationapparatus according to claim 4, wherein the control apparatus is anotherbase station apparatus.
 6. The base station apparatus according to claim4, wherein the control apparatus decides, whether the state of each cellof the one or more cells to be off or on, based on a traffic load.
 7. Amethod for a control apparatus controlling a base station apparatusserving one or more cells, the method comprising: receiving, via aninterface between the control apparatus and the base station apparatus,cell information from the base station apparatus, the cell informationincluding one or more cell identities respectively corresponding to theone or more cells; deciding whether a state of each cell of the one ormore cells is to be off or on; assigning, to the one or more cells, oneor more subframes in which one or more synchronization signals are nottransmitted, the one or more synchronization signals being transmittedon other subframes than the assigned one or more subframes; andnotifying the base station apparatus of information indicating theassigned one or more subframes where the one or more synchronizationsignals are not transmitted.
 8. The method according to claim 7, whereinthe control apparatus is another base station apparatus.
 9. The methodaccording to claim 7, wherein the deciding, whether the state of eachcell of the one or more cells is to be off or on, is based on a trafficload.
 10. A method for a base station apparatus from among one or morebase station apparatuses controlled by a control apparatus, the methodcomprising: serving one or more cells, and sending, via an interfacebetween the control apparatus and a base station apparatus, cellinformation to the control apparatus, the cell information including oneor more cell identities respectively corresponding to the one or morecells, wherein a state of each cell of the one or more cells is decidedto be off or on by the control apparatus, one or more subframes, inwhich one or more synchronization signals are not transmitted, areassigned to the one or more cells by the control apparatus, the one ormore synchronization signals being transmitted on other subframes thanthe assigned one or more subframes, and the method further comprisesreceiving, from the control apparatus via the interface, informationindicating the assigned one or more subframes where the one or moresynchronization signals are not transmitted.
 11. The method according toclaim 10, wherein the control apparatus is another base stationapparatus.
 12. The method according to claim 10, wherein the deciding,whether the state of each cell of the one or more cells to be off or on,is based on a traffic load.